[tbb-dev] Thoughts about future Tor Browser plans

[Matthew Finkel]

Hi everyone,

(tldr; read the last paragraph)

In October [0] we were very excited about the prospect of all Tor
Browser platforms following the Firefox Rapid Release schedule. However,
in April (now), Android is still the only platform following the rapid
release train and Windows, macOS and Linux remain on the extended
support release (ESR).

As we move closer to the next ESR transition, this year it is beginning
at Firefox 91 in May [1], I am wondering whether we should reverse
course and slow down. At this point, we cannot safely transition all
platforms onto the rapid release train before October (when 78esr
reaches its EOL), so the only option is moving all desktop platforms
onto FF91esr and then evaluate migrating onto the rapid release train
after that.

Unfortunately, we are still a very small team, and the current situation
is already pushing our team to its limits. Yesterday I spoke with Georg
about another subject, and he briefly mentioned the idea of keeping the
desktop platforms on ESR instead of moving onto the rapid releases. This
alone wouldn't make much difference, and I previously discarded this
idea, because we're already fighting all of the code churn for Android
(although some of the code, like the automatic updater, is not used on
Android). The important piece of this plan is reducing Fenix's burden,
too. 

My current thought is that we move desktop platforms from 78esr to
91esr, and we begin rebasing our Fenix branches (and dependencies) only
every 2-3 months. The only exception is geckoview where we continue
rebasing our geckoview branches on the existing schedule. In addition,
we drop desktop patches from the geckoview branches, and Android patches
from the ESR branches. We could've (and should've) done the latter
simplification earlier, but the former change makes future ESR
transitions a little more complicated. I think we can live with that.

- Matt

[0] https://lists.torproject.org/pipermail/tbb-dev/2020-October/001154.html
[1] https://wiki.mozilla.org/Release_Management/Calendar